[zfs-discuss] zfs/lofi/share panic

from
[Frank Middleton]

Subject:

[zfs-discuss] zfs/lofi/share panic

From:

Frank Middleton

Date:

Mon, 24 May 2010 16:52:17 -0400

Many many moons ago, I submitted a CR into bugs about a
highly reproducible panic that occurs if you try to re-share
a lofi mounted image. That CR has AFAIK long since
disappeared - I even forget what it was called.
This server is used for doing network installs. Let's say
you have a 64 bit iso lofi-mounted and shared. You do the
install, and then wish to switch to a 32 bit iso. You unshare,
umount, delete the loopback, and then lofiadm the new iso,
mount it and then share it. Panic, every time.
Is this such a rare use-case that no one is interested? I have
the backtrace and cores if anyone wants them, although
such were submitted with the original CR. This is pretty
frustrating since you start to run out of ideas for mountpoint
names after a while unless you forget and get the panic.
FWIW (even on a freshly booted system after a panic)
# lofiadm zyzzy.iso /dev/lofi/1
# mount -F hsfs /dev/lofi/1 /mnt
mount: /dev/lofi/1 is already mounted or /mnt is busy
# mount -O -F hsfs /dev/lofi/1 /mnt
# share /mnt
#
If you unshare /mnt and then do this again, it will panic.
This has been a bug since before Open Solaris came out.
It doesn't happen if the iso is originally on UFS, but
UFS really isn't an option any more. FWIW the dataset
containing the isos has the sharenfs attribute set,
although it doesn;t have to be actually mounted by
any remote NFS for this panic to occur.
Suggestions for a workaround most welcome!
Thanks
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